A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g., comprising part of, one or several dies) on a substrate (e.g., a silicon wafer) that has a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are successively exposed.
Known lithographic apparatus include so-called scanners, in which each target portion is irradiated by scanning the mask through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti parallel to this direction. After each scan the direction of scanning movement of the mask and the direction of scanning movement of the substrate is reversed. The substrate is also moved transverse to the scanning direction. These movements are time consuming and thus have a detrimental impact on the throughput of the lithographic apparatus (i.e., the number of substrates exposed per hour by the lithographic apparatus).